Proper alignment between a wheel hub and a brake drum is an important consideration when installing the brake drum onto the wheel hub, particularly regarding a heavy vehicle such as a truck. Misalignment causes vibration, shimmy, excessive brake wear, and possible breakage of the drum or hub. Even if the drum is off-center by only 1/16", these problems can occur. Errors in alignment of such a small magnitude are often very difficult to detect when the brake drum is being installed. Thus, means for ensuring proper alignment between the brake drum and wheel hub during installation is needed.
Conventional wheel hubs have hub mounting assemblies which include a wheel bolt for securing a brake drum and wheel onto the hub, a first hub pilot for guiding installation of the wheel onto the hub, and a second hub pilot for guiding installation of the brake drum onto the hub. The first and second hub pilots generally comprise radial guide surfaces confronting the wheel bolt. Typically, the second hub pilot has a larger diameter than the first hub pilot (measured from the center of the wheel hub). The second hub pilot is defined by a corner edge which is set back from the mounting side of the hub such that the first hub pilot sits between the second hub pilot and the mounting side of the hub.
Brake drums have a plurality of drum mounting means which mate with the hub mounting assemblies to hold the brake drum on the hub. A conventional drum mounting means comprises an aperture for receiving the wheel bolt and a drum pilot near the aperture and configured to engage the second hub pilot to guide the brake drum onto the hub. The drum pilot typically comprises a radial surface with a beveled front edge.
When mounting the brake drum onto the hub, it is possible for the beveled front edge of one or more of the drum pilots to catch on one of the corner edges which defines one of the hub pilots. If less than all of the drum pilots are caught, the brake drum is eccentrically mounted relative to the rotational center of the wheel. If all drum pilots are caught, then the drum will be improperly spaced from the hub. Thus, there is a need for an improved drum mounting means for ensuring proper alignment and installation of a brake drum onto a wheel hub.